One such known spinner is shown diagrammatically in plan view in FIG. 1, installed in a vessel.
In a water meter, such a spinner 1 is disposed in a cylindrical portion, referred to as a chamber, of a vessel 2 that provides a leaktight connection with water inlet and outlet pipes. The spinner is mounted on an axis of rotation 3 substantially centered on the chamber, and the water entering via the inlet tube 4 of the vessel drives the spinner in rotation and then leaves via the outlet tube 5 of the vessel.
The inclination of the spinner blades is selected so as to reduce the opposing hydraulic torque. The number of spinner blades is selected as a function of the chamber so as to ensure that there is always at least one driving blade.